"I am reminded by a lot of things. A lot of good memories we had," Rihanna says of Brown. "By the slightest things: hotel rooms, tour venues. Any little thing: music, songs. And I do miss him at times."

Brown accepted a plea deal of community labor, five years' formal probation and domestic violence counseling after physically assaulting the "We Found Love" singer in February 2009. Rihanna likens the entire experience to "a circus."

As Brown's public image took a hit, "I felt protective," Rihanna admits. "I felt like the only person they hate right now is him. It was a weird, confusing space to be in. As angry as I was, as angry and hurt and betrayed, I just felt like he made that mistake because he needed help ... and who's going to help him?"

"Nobody's going to say he needs help," Rihanna adds. "Everybody's going to say he's a monster without looking at the source . . . and I was more concerned about him."

Calling the ordeal "embarrassing" and "humiliating," Rihanna tells Winfrey it's been difficult to let Brown go. "I lost my best friend. Everything I knew switched, switched in a night, and I couldn't control that."